"Are ye not more to me than my own affairs, and even life!" he went on. "Come, listen to me! I am six years older than you, and Mr. Boldwood is ten years older than I, and consider—I do beg of 'ee to consider before it is too late—how safe you would be in his hands!"
This is so selfless, and should show Bathsheba that Oak's intentions are in the right place. He's not trying to compete with Troy. He simply wants the best for the woman he loves